Method and a circuit arrangement for signal processing in a telecommunication system

• US 6,061,385 A
• Filed: 03/10/1997
• Issued: 05/09/2000
• Est. Priority Date: 03/12/1996
• Status: Expired due to Fees

• Current Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Ostman, Kjell
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): PARK, ALBERT C
• Application Number:
  US08/814,448
• Time in Patent Office: 1,156 Days
• Field of Search: 375/316, 375/200, 375/206, 329/315, 329/316, 455/31.4, 455/34.1, 455/553
• US Class Current: 375/130
• CPC Class Codes: H04B 1/00 Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453

Abstract

The object of the invention is a method and a circuit arrangement for processing a spread spectrum signal and a frequency modulated signal. According to the invention the radio frequency signal is received (1, 2), the received signal is converted into an intermediate frequency signal (3, 4a, 4b), and then an intermediate frequency signal processing (6, 30, 31, 40) is made and the processed intermediate frequency signals are converted (32, 42a, 42b) into baseband signals. The signal derived from the received signal is converted (41) into a digital sampled signal which is processed (32, 42a, 42b, 111, 120, 121) digitally, whereby the either a signal derived from the received spread spectrum signal or a signal derived from the received frequency modulated signal, respectively, is selected (5) as the signal which is converted to the digital sampled signal. According to the invention the same intermediate frequency and baseband components (6, 7, 30, 31, 40, 41) can be used to process both the spread spectrum signal and the frequency modulated signal.

Claims

1. A method for processing a received spread spectrum signal and a received frequency modulated signal, in which:

a radio frequency signal is received (1,

     2), the received radio frequency signal being either a spread spectrum signal or a frequency modulated signal,

the received signal is converted into an intermediate frequency signal (3, 1. IF),

an intermediate frequency signal processing is performed (4a, 4b) to provide processed intermediate frequency signals, comprising the following steps, namely;

a frequency modulated intermediate frequency signal is formed by use of a first band-pass filter (4a), and spread spectrum intermediate frequency signal is formed by use of a second band-pass filter (4b),

with respect to the derived signals, either a signal derived from the received spread spectrum signal or the signal derived from the received frequency modulated signal, respectively, is selected by switching means (5), and

the signal selected by said switching means, or a signal derived from it, is converted into a second intermediate frequency signal (2. IF) by use of converting means (6,

     7),

a speech signal is added to said first intermediate signal or to said second intermediate signal in order to form a sum signal by use of adding means (40),

a sampled signal from said sum signal is formed by use of sampling means (41),

the sampled intermediate frequency signals are converted into baseband signals, comprising the following steps, namely the spread spectrum signal or the frequency modulated signal is converted into a baseband signal by use of converting means (32, 42a, 42b), the spread spectrum signal is digitally filtered by filtering means (43a, 43b), the spread spectrum of the filtered spread spectrum signal is despread by use of despreading means (118a, 118b,

     119), the frequency modulated signal is digitally demodulated by use of demodulating means (33), and the sampled signal is filtered by use of filter means (44) in order to separate the speech signal from the intermediate frequency signal.

2. A method for processing a received spread spectrum signal and a received frequency modulated signal, in which:

a radio frequency signal is received (1,

     2), the received radio frequency signal being either a spread spectrum signal or a frequency modulated signal,

the received signal is converted into an intermediate frequency signal (3, 1. IF),

an intermediate frequency signal processing is performed (4a, 4b) to provide processed intermediate frequency signals, comprising the following steps, namely;

a frequency modulated intermediate frequency signal is formed by use of a first band-pass filter (4a), and spread spectrum intermediate frequency signal is formed by use of a second band-pass filter (4b),

with respect to the derived signals, either a signal derived from the received spread spectrum signal or the signal derived from the received frequency modulated signal, respectively, is selected by switching means (5),

the signal selected by said switching means, or a signal derived from it, is converted into a second intermediate frequency signal (2. IF) by use of converting means (6,

     7),

the frequency modulated second intermediate frequency signal is demodulated by demodulating means (10),

with respect to the signals derived from the second intermediate frequency signals, either a signal derived from the received spread spectrum signal or the signal derived from the received frequency modulated signal, respectively, is selected by switching means (5),

a speech signal is added to said first intermediate signal or to said second intermediate signal in order to form a sum signal by use of adding means,

a sampled signal from said sum signal is formed by use of sampling means (14),

the sampled intermediate frequency signals are converted into baseband signals, comprising the following steps, namely the spread spectrum signal is converted into a baseband signal by use of converting means, the spread spectrum signal is digitally filtered by filtering means, the spread spectrum of the filtered spread spectrum signal is despread by use of despreading means, and the sampled signal is filtered by use of filter means in order to separate the speech signal from the intermediate frequency signal.

3. A circuit arrangement for processing a received spread spectrum signal and a received frequency modulated signal, the circuit arrangement comprising:

means (1, 2,

     3) to receive radio frequency signals, and including first conversion means (3) to convert the received signals into intermediate frequency signals,

first processing means (4a, 4b, 6, 7, 30,

     31) to process the intermediate frequency signals to provide processed intermediate frequency signals, comprising;

a first band-pass filter (4a) to form a frequency modulated intermediate frequency signal, and a second band-pass filter (4b) to form a spread spectrum intermediate frequency signal,

first switching means (5), which is connected to output terminals of said first and said second band-pass filters for selecting either said frequency modulated intermediate frequency signal or said spread spectrum intermediate frequency signal, and

second conversion means (6,

     7) to convert the signal selected by said switching means, or a signal derived from it, into a second intermediate frequency signal,

said circuit arrangement further comprises sampling means (14) to convert the second intermediate frequency signal into a digital sampled signal,

wherein said sampling means (14) have a sampling frequency, which is four times the intermediate frequency of said second intermediate frequency signal (IF2), the sampling frequency of said sampling means is a multiple of a symbol frequency of the spread spectrum signal, and said multiple is eight,

third conversion means (33,

     15) to convert the sampled intermediate frequency signals into baseband signals,

wherein said third conversion means further comprises means (33) to digitally demodulate the frequency modulated signal, and

wherein said third conversion means further comprises despread means to convert the sampled intermediate frequency spread spectrum signal into a despread baseband signal, the despread means comprising;

means (16,

     20) to select two consecutive samples out of eight samples input from said sampling means (14),

means (26) to add a first sample (I1) of said consecutive samples into a first register (26) or to subtract the first sample from the first register, based on a first PN sequence (PN I),

means (23) to invert a second PN sequence (PN Q),

means (21, 23, 24,

     26) to add the second sample (Q1) of said two consecutive samples into the first register (26) or to subtract the second sample from the first register, based on an inverted bit contained in the second PN sequence (PN Q),

means (22, 25,

     28) to add the first sample (I1) into a second register (28) or to subtract the first sample from the second register, based on the second PN sequence (PN Q), and

means (22, 25,

     28) to add the second sample (Q1) into the second register (28) or to subtract the second sample from the second register, based on a bit contained in the first PN sequence (PN I).

4. The use of the circuit arrangement according to claim 3, in an AMPS system, and wherein the digital-to-analog converter is operated at a sampling speed and a number of bits of resolution to enable use of the analog-to-digital converter for both of the spread spectrum signal and the frequency modulated signal.

5. A circuit arrangement for processing a received spread spectrum signal and a received frequency modulated signal, the circuit arrangement comprising:

means to receive radio frequency signals, and including first conversion means to convert the received signals into intermediate frequency signals,

first processing means to process the intermediate frequency signals to provide processed intermediate frequency signals, comprising;

a first band-pass filter to form a frequency modulated intermediate frequency signal, and a second band-pass filter to form a spread spectrum intermediate frequency signal,

first switching means, which is connected to output terminals of said first and said second band-pass filters for selecting either said frequency modulated intermediate frequency signal or said spread spectrum intermediate frequency signal,

second conversion means to convert the signal selected by said switching means, or a signal derived from it, into a second intermediate frequency signal,

means to demodulate the frequency modulated signal,

said circuit arrangement further comprises second switching means for selecting either the frequency modulated intermediate frequency signal or the spread spectrum intermediate frequency signal,

sampling means connected to an output terminal of said second switching means to sample the selected signal,

wherein said sampling means have a sampling frequency, which is four times the intermediate frequency of said second intermediate frequency signal, the sampling frequency of said sampling means is a multiple of a symbol frequency of the spread spectrum signal, and said multiple is eight,

third conversion means to convert the spread spectrum signal sampled intermediate frequency signals into baseband signals,

despread means to convert the sampled intermediate frequency spread spectrum signal into a despread baseband signal, the despread means comprising;

means to select two consecutive samples out of eight samples input from said sampling means,

means to add a first sample of said consecutive samples into a first register or to subtract the first sample from the first register, based on a first PN sequence,

means to invert a second PN sequence,

means to add the second sample of said two consecutive samples into the first register or to subtract the second sample from the first register, based on an inverted bit contained in the second PN sequence,

means to add the first sample into a second register or to subtract the first sample from the second register, based on the second PN sequence, and

means to add the second sample into the second register or to subtract the second sample from the second register, based on a bit contained in the first PN sequence.

6. The use of the circuit arrangement according to claim 5 in an AMPS system, and wherein the digital-to-analog converter is operated at a sampling speed and a number of bits of resolution to enable use of the analog-to-digital converter for both of the spread spectrum signal and the frequency modulated signal.

7. A circuit arrangement for processing a received spread spectrum signal and a received frequency modulated signal, the circuit arrangement comprising:

means to receive radio frequency signals, and including first conversion means to convert the received signals into intermediate frequency signals,

first processing means to process the intermediate frequency signals to provide processed intermediate frequency signals, comprising;

a first band-pass filter to form a frequency modulated intermediate frequency signal, and a second band-pass filter to form a spread spectrum intermediate frequency signal,

first switching means, which is connected to output terminals of said first and said second band-pass filters for selecting either said frequency modulated intermediate frequency signal or said spread spectrum intermediate frequency signal, and

second conversion means to convert the signal selected by said switching means, or a signal derived from it, into a second intermediate frequency signal,

said circuit arrangement further comprises means to add a speech signal to said first intermediate frequency signal or to said second intermediate frequency signal in order to form a sum signal,

sampling means to convert the second intermediate frequency signal into a digital sampled signal,

wherein said sampling means is operative to form a sampled signal from said sum signal,

third conversion means to convert the sampled intermediate frequency signals into baseband signals,

wherein said third conversion comprises means to digitally filter the spread spectrum signal, means to despread the spread spectrum of the filtered spread spectrum signal, means to digitally demodulate the frequency modulated signal, and means to filter the sampled signal in order to separate the speech signal from the intermediate frequency signal.

8. A circuit arrangement according to claim 7, wherein said sampling means have a sampling frequency, which is four times the intermediate frequency of said second intermediate frequency signal, the sampling frequency of said sampling means is a multiple of a symbol frequency of the spread spectrum signal.

9. A circuit arrangement according to claim 8, wherein said multiple is eight.

10. A circuit arrangement for processing a received spread spectrum signal and a received frequency modulated signal, the circuit arrangement comprising:

means to receive radio frequency signals, and including first conversion means to convert the received signals into intermediate frequency signals,

first processing means to process the intermediate frequency signals to provide processed intermediate frequency signals, comprising;

a first band-pass filter to form a frequency modulated intermediate frequency signal, and a second band-pass filter to form a spread spectrum intermediate frequency signal,

first switching means, which is connected to output terminals of said first and said second band-pass filters for selecting either said frequency modulated intermediate frequency signal or said spread spectrum intermediate frequency signal, and

second conversion means to convert the signal selected by said switching means, or a signal derived from it, into a second intermediate frequency signal,

means (10) to demodulate the frequency modulated signal,

said circuit arrangement further comprises second switching means (13) for selecting either the frequency modulated intermediate frequency signal or the spread spectrum intermediate frequency signal,

means to add a speech signal to said first intermediate frequency signal or to said second intermediate frequency signal in order to form a sum signal,

sampling means connected to an output terminal of said second switching means to sample the selected signal,

wherein said sampling means is operative to form a sampled signal from said sum signal,

third conversion means to convert the sampled intermediate frequency signals into baseband signals,

wherein said third conversion means comprises means to digitally filter the spread spectrum signal, means to despread the spread spectrum of the filtered spread spectrum signal, and means to filter the sampled signal in order to separate the speech signal from the intermediate frequency signal.

11. A circuit arrangement according to claim 10, wherein said sampling means have a sampling frequency, which is four times the intermediate frequency of said second intermediate frequency signal, and the sampling frequency of said sampling means is a multiple of a symbol frequency of the spread spectrum signal.